This invention relates generally to hydraulic systems for engines, and more particularly to a device and method for replenishing fluid loses in a common rail for an engine hydraulic system.
An example of a typical hydraulic system for an engine might be a set of hydraulically actuated fuel injectors that utilize engine lubricating oil as their actuation fluid medium. It has long been known that engine lubricating oil expands and contracts as much as 15% or more in volume over the expected temperature range that the engine will encounter. For instance, an engine can fall to relatively low temperatures, possibly below 0xc2x0 F., when not running in a low temperature environment, and can experience substantially higher temperatures when running for a prolonged period in a relatively warm ambient environment. When an engine is running and for some duration after being shut down, the hydraulic systems for the engine will be substantially completely full of lubricating oil. However, as the engine cools, the lubricating oil in the hydraulic system tends to contract and create fluid voids in such areas as the common rail and/or pump priming reservoir of the hydraulic system. While the formation of these fluid voids is expected and not harmful to the engine or hydraulic system, some undesirable results can occur. For instance, when the engine is restarted after a substantial cooling period, a sometimes annoying excessive cranking of the engine is required in order to bring the hydraulic system back up to full pressure to start the engine anew. While this excessive cranking is not indicative of an actual problem, it can be misperceived as a problem by the engine user.
The present invention is directed to these and other problems associated with replenishing fluid in engine hydraulic systems.
In one aspect, an engine includes a valve cover attached to a head to define a chamber. A replenishing reservoir is fluidly connected to the chamber and a common rail of a hydraulic system via a replenishing conduit. A check valve is positioned in the replenishing conduit.
In another aspect, a method of replenishing oil in a hydraulic system of a engine includes a step of capturing an amount of oil in a replenishing reservoir fluidly connected to a chamber defined by the engine head and valve cover. The replenishing reservoir is fluidly connected to a common rail of a hydraulic system attached when pressure in the common rail is less than pressure in the chamber.
In still another aspect, an oil circulation system for an engine includes a lubricating oil circuit with a circulation passageway. A portion of the circulation passageway is a chamber defined by the engine head and valve cover. A hydraulic system includes a common rail fluidly connected to a plurality of hydraulic devices, a replenishing reservoir fluidly connected to the chamber, and a replenishing conduit extending between the common rail and the replenishing reservoir. A valve is positioned to close the replenishing conduit when fluid pressure in the common rail is substantially greater than fluid pressure in the chamber.